Re: [Django] #27340: Model pre_init signal should provide an `instance` argument

[Django]

#27340: Model pre_init signal should provide an `instance` argument
-+-
 Reporter:  Ask Solem Hoel   |Owner:  nobody
 Type:  New feature  |   Status:  closed
Component:  Database layer   |  Version:  1.10
  (models, ORM)  |
 Severity:  Normal   |   Resolution:  needsinfo
 Keywords:   | Triage Stage:
 |  Unreviewed
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-

Comment (by Ask Solem Hoel):

 lol, you want an example.  Brace yourself, will probably be more difficult
 to understand, but here:

 https://github.com/robinhood/thorn/blob/master/thorn/django/signals.py#L39-L44

 we use the pre)save signal to store a snapshot of how the model looked
 like before it was changed


 With the proposed change we'd be able to avoid doing two database queries
 for every Model.save by doing this:


 @signals.pre_init.connect
 def _track_changes(instance, args, kwargs, **kwargs):
 instance._original_args = args, kwargs

 There's no other way as far as I can find, as we don't want to monkeypatch
 Model, and in any case it's very strange that the pre_init signal omits
 the instance being created.

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Re: [Django] #27340: Model pre_init signal should provide an `instance` argument

[Django]

#27340: Model pre_init signal should provide an `instance` argument
-+-
 Reporter:  Ask Solem Hoel   |Owner:  nobody
 Type:  New feature  |   Status:  closed
Component:  Database layer   |  Version:  1.10
  (models, ORM)  |
 Severity:  Normal   |   Resolution:  needsinfo
 Keywords:   | Triage Stage:
 |  Unreviewed
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-
Changes (by Tim Graham):

 * status:  new => closed
 * resolution:   => needsinfo


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Re: [Django] #27340: Model pre_init signal should provide an `instance` argument

[Django]

#27340: Model pre_init signal should provide an `instance` argument
-+-
 Reporter:  Ask Solem Hoel   |Owner:  nobody
 Type:  New feature  |   Status:  new
Component:  Database layer   |  Version:  1.10
  (models, ORM)  |
 Severity:  Normal   |   Resolution:
 Keywords:   | Triage Stage:
 |  Unreviewed
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-

Comment (by Tim Graham):

 Could you provide an example of your existing code and what it would look
 like after this change? I'll check that I don't see another way to
 accomplish your use case.

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Re: [Django] #27340: Model pre_init signal should provide an `instance` argument

[Django]

#27340: Model pre_init signal should provide an `instance` argument
-+-
 Reporter:  Ask Solem Hoel   |Owner:  nobody
 Type:  New feature  |   Status:  new
Component:  Database layer   |  Version:  1.10
  (models, ORM)  |
 Severity:  Normal   |   Resolution:
 Keywords:   | Triage Stage:
 |  Unreviewed
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-
Changes (by Ask Solem Hoel):

 * needs_docs:   => 0
 * needs_better_patch:   => 0
 * component:  Uncategorized => Database layer (models, ORM)
 * needs_tests:   => 0
 * type:  Uncategorized => New feature


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[Django] #27340: Model pre_init signal should provide an `instance` argument

[Django]

#27340: Model pre_init signal should provide an `instance` argument
+
 Reporter:  Ask Solem Hoel  |  Owner:  nobody
 Type:  Uncategorized   | Status:  new
Component:  Uncategorized   |Version:  1.10
 Severity:  Normal  |   Keywords:
 Triage Stage:  Unreviewed  |  Has patch:  0
Easy pickings:  0   |  UI/UX:  0
+
 I struggle to find reasons as to why this argument is ommitted.

 The current signature for pre_init is:

 {{{
 class Model(six.with_metaclass(ModelBase)):
 _deferred = False

 def __init__(self, *args, **kwargs):
 signals.pre_init.send(sender=self.__class__, args=args,
 kwargs=kwargs)
 }}}

 I suggest that the signature should be:

 {{{
 class Model(six.with_metaclass(ModelBase)):
 _deferred = False

 def __init__(self, *args, **kwargs):
 signals.pre_init.send(sender=self.__class__, args=args,
 kwargs=kwargs, instance=self)
 }}}

 Or alternatively, that the `post_init` signal contains the args and kwargs
 used to construct the model.

 The reason for wanting access to the instance in pre_init is that I want
 to track changes
 to the model since it was first retrieved from the database - This is
 currently not possible without subclassing Model,
 and that is not a realistic option for us as we deal with third party
 models.

 The current way we handle this is by using `pre_save` to fetch the row
 from the database again, but this is suboptimal
 and this a simple change would allow us to do this.

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